code: def test_underscore_docstring(en_vocab):
      """Test that docstrings are available for extension methods, even though
      they're partials."""
  
      def test_method(doc, arg1=1, arg2=2):
          """I am a docstring"""
          return (arg1, arg2)
  
      Doc.set_extension("test_docstrings", method=test_method)
      doc = Doc(en_vocab, words=["hello", "world"])
      assert test_method.__doc__ == "I am a docstring"
      assert (
          doc._.test_docstrings.__doc__.rsplit(". ")[-1]
          == "I am a docstring"
      )
  
file_path: spacy/spacy/tests/doc/test_underscore.py
imports: import pytest
  from mock import Mock
  from spacy.tokens import Doc, Span, Token
  from spacy.tokens.underscore import Underscore
label_desc: Use image node_id 14 for calling a global function with example usage: test_underscore_docstring(en_vocab) and returns: arg1,  arg2